This tag is meant for everything that has to do with mathematical operations. So if you want to ask a question about doing calculations in `awk`, or if you have a question about `bc`, this is the right tag to use.

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1answer
37 views

“) Syntax error Invalid arithmetic operator (error token is ”

I have commands in a bash script getting data from a source text file and then adding the value of a variable to it and using it in an if/else condition. Source data file (db_count.ini) (Note: ...
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2answers
95 views

what's the simplest way to increment the numbers in this string 01:02:99 in unix?

What is the simplest way to increment the numbers in this string 01:02:99? Expected output: 01:03:00 I'm hoping for a sed response, but I don't think it would be simple.
0
votes
1answer
403 views

Why does the factor command produce nonsense on an RSA modulus?

Ok, so I think I may have found a flaw in... something. I honestly don't know. This is such a weird scenario. I was attempting to break very small asymmetric (RSA) encryption, just as a Proof of ...
0
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1answer
60 views

Bash script to add or subtract two numbers from user input

I am very new to Linux and am taking a course in it. Very excited to learn more. I am working on a script that asks user for two numbers, then asks whether user wants to add or subtract. I failed the ...
0
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1answer
56 views

How does this equation gives numbers random between two values?

How does this equation gives random numbers between max and min divisible by divisibleBy echo $(((RANDOM%(max-min+divisibleBy))/divisibleBy*divisibleBy+min))
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1answer
46 views

Arithmetic expressions in for-loop

In for (( expr1 ; expr2 ; expr3 )) ; do commands ; done expr1, expr2, and expr3 are arithmetic expressions. Is expr1 ; expr2 ; expr3 not an arithmetic expression? (( expr1 ; expr2 ; expr3 )) isn'...
0
votes
3answers
109 views

Comparing integers: arithmetic expression or conditional expression

In Bash, two integers can be compared using conditional expression arg1 OP arg2 OP is one of ‘-eq’, ‘-ne’, ‘-lt’, ‘-le’, ‘-gt’, or ‘-ge’. These arithmetic binary operators return true if ...
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1answer
34 views

Arithmetic expansion and parameter expansion

$ x=foo; foo=bar; bar=6; $ echo $x foo $ echo $((x)) 6 why can the arithmetic expansion trace from variable x to its value foo, from variable foo to its value bar, and then from variable foo to ...
3
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1answer
171 views

Variables of integer type in Bash?

There are two ways to define and use variables of integer type in Bash declare -i a new variable use a variable in an arithmetic expression, without declaring it. My questions: What are the ...
-2
votes
1answer
40 views

Is a string an arithmetic expression?

In Bash, I use a string where an arithmetic expression is expected: $ (( hello )) $ echo $? 1 $ echo $(( hello )) 0 $ let aaa=hello $ echo $? 1 $ echo $aaa 0 There is no error reported. So is a ...
2
votes
1answer
31 views

Bash shell script program that prompts for and reads two integers from the user.

Okay, so I been trying to figure this problem for a while and I'm coming up with errors left and right. This is my first time trying to learn the basics. So any advice would be helpful! Problem: I'm ...
0
votes
2answers
39 views

Sed incremental arithmetic

I want to replace a number at the end of a string by incrementing the number by one each time I run a specific sed line. the string looks like this: server-port=25555 I was thinking I could run ...
2
votes
1answer
85 views

Why do newer version of awk print large integers instead of decimals?

I often use the awk (gawk) calculator: calc(){ awk "BEGIN{ print $* }" ;} In Ubuntu 14.04, it output big numbers in standard form, e.g. $ calc 56777654409823*4674990588446667952594759939814064128 ...
3
votes
2answers
162 views

What does the comma operator do in Bash arithmetic?

In Bash Manual, sec 6.5 Shell Arithmetic expr1 , expr2 comma What does the comma operator do? Are expr1 and expr2 arithmetic expressions?
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2answers
32 views

Does command substitution within arithmetic substitution get word split?

I seem to recall from comments on this site that the contents of arithmetic expansion may be word split, but I can't find the comment again. Consider the following code: printf '%d\n' "$(($(sed -n '/...
0
votes
1answer
34 views

Arithmetic syntax error with a number variable

I am having a difficulty with an arithmetic syntax error. I am reading the name of text files from the command line and count the number of the lines of each file. NUM=$(wc -l "$text") and then I ...
0
votes
1answer
47 views

Convert a column of epochs into a time column starting from 0

What I have Hi, imagine a lot of this files, where first column is epoch, and the other(s) column(s) are some data: 1000333,34,1 1001456,56,0 1005356,34,2 What I need I need to transform them ...
0
votes
1answer
38 views

awk: arithmetic does not work on a particular field

I have several lines such as: N2O + M = N2 + O + M 1.300E+11 0.00 59620.0 I need to substitute the third from last field with a factor of itself which does not work ...
3
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0answers
72 views

Shell Arithmetic Expansion with Quotes

In Bash and Dash, using quotes in an Arithmetic Expansion is illegal: $ bash -c 'x=123;echo $(("$x"))' bash: "123": syntax error: operand expected (error token is ""123"") $ dash -c 'x=123;echo $(("$...
3
votes
3answers
54 views

How to treat numbers starting with zeroes as decimal integer

Input would be file name like following : A-B-000001-C A-B-000002-C ..... ..... A-B-999999-C All file should be sequential. I want to find missing sequential file names. For this I'm separating 6 ...
0
votes
1answer
115 views

arithmetic operation with columns in text file

I have a data file which consists of two columns. I need to perform arithmetic operation with these columns as follows; column_1=a(i) column_2=b(i) where i is the line number result_1=a(1)*100/b(...
1
vote
1answer
87 views

Find a “moderately large” divisor of a given number?

After processing some data, I get out a file that has a certain number of data points in it --- one per line. I need to pass these data points on to another tool that will do more number crunching --- ...
2
votes
2answers
151 views

Help with script reading numbers from a file and determining if they are even or odd numbers

So I want my script to test for the existence of a file which I already populated with numbers. It does that, but after it does that I want it to run a while look checking to see if the numbers in the ...
1
vote
1answer
33 views

Modify a commands to an original values

I am working with terminal in Linux and have some problems. I need to make a script contains these commands in pico and then to execute it. I've already done this and my output is 254 9 23 -45 and ...
0
votes
2answers
240 views

How to increment local variable in Bash?

Data 1 \begin{document} 3 Code #!/bin/bash function getStart { local START="$(awk '/begin\{document\}/{ print NR; exit }' data.tex)" echo $START } START2=$(getStart) echo $...
0
votes
1answer
45 views

I'm trying to write a script to compare results from a code to my already established results for regression testing

I've been trying to write a bash script to run my code, then compare the final output to a previous run (with the correct result) under regression.dat. The goal is for it to tell me if the code ...
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4answers
116 views

Show ratio for all available resolutions

I tried to get the ratio with this script: echo "$(xrandr)"|cut -f 4 -d" "|sed 's/x/00 \\\* /g'|while read i; do echo "$i = "$(expr $i); done but I get errors like 102400 * 768 = expr: ...
3
votes
2answers
585 views

Subtract floating numbers in shell script

I'm trying to do some calculation in shell script with CPU usage. Which return floating point number. But when I subtract this number I'm getting error. See the following code and error. Code #!/bin/...
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2answers
377 views

Copy Single Value from a file to a variable and perform arithmetic over it? [duplicate]

Suppose we have a file like 'abc.txt' which has a single value 123456 and file 'xyz.txt' which also has a single value like 654321. I want to store these values form the file to some shell variable ...
1
vote
1answer
46 views

Add list of numbers like an accountant

How can I add a list of numbers like an accountant would (using presumably bc or dc)? Typically this is done by entering each number followed by a "+" key, e.g., there would be on an adding machine. I ...
1
vote
1answer
85 views

Loop over lines of file, partition file and classify each partition

In the following I've put up my code for iterating over lines of a file in order to collect data within a segment from the file in following fashion: Illustration for understanding procedure: segL ...
1
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1answer
159 views

increment a value pulled from a file

I have a cron that I am writing that will repeat every hour, and I need a simple way to pass a counter from the last run to the next run. My plan was to add the number to a file at the end, and then ...
2
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2answers
377 views

Assign variable identifier in loop and echo its value

I hope this question is not a duplicate because I've been trying various ways to solve this problem but couldn't find any solution. I have a for loop in which I'd like to store a command output into ...
25
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2answers
2k views

What does a dollar sign followed by a square bracket mean in bash?

It appears that $[expr] performs arithmetic expansion just like $((expr)). But I can't find any mention of $[ in the bash manual. This command gives no results: gunzip -c /usr/share/man/man1/bash.1....
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votes
4answers
336 views

Hexadecimal number sequence checker in Linux?

I have a list of hexadecimal number. I would like to check whether they are in sequence or not. That is, they should be consecutive numbers, in increasing order. In other words, there should be an ...
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2answers
629 views

Aliasing using for or while loop in .bashrc

Can I use a for or while loop when I have similar pattern in the aliases that I put in my .bashrc file? For example, I have: alias c0='ssh computer-1-0' alias c1='ssh computer-1-1' alias c2='ssh ...
2
votes
1answer
162 views

bash + how to calculate very long numbers in bash? [duplicate]

how to calculate very long numbers in bash? param=$(( 3247238523785623478565 + 53453453252345346534563412634 )) echo $param 3420247196502465471 as we see here this isnt the right answer , because ...
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1answer
165 views

bash: -eq vs. == and `bc` output type

This snippet of code has been taken from a larger script, (humbly) simulating the non-existing abs() function: [[ $(echo "$val < 0" | bc) -eq 1 ]] && val=$(echo "$val * -1" | bc) So we ...
3
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1answer
58 views

Moving sub-directory to new parent directory where the new directory name is incremented by 1

I am attempting to move a sub-directory from one parent directory to another for hundreds of instances, while changing the name of the sub-directory during the move. My directories are a set of ...
0
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2answers
98 views

Script with multiple arithmetic conditions failing

I'm experiencing problems with a script converting numbers to bytes. If the number is large enough to hit gigabytes or terabytes, the script runs as it should. If the number converts to kilobytes, ...
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vote
2answers
2k views

How to format decimal number to display the preciding zero but not the trailing ones?

I have the following script on Ubuntu 14.04.1 LTS 64-bit bash command prompt: S=0.030 F=0.150 N=10 reso=20 DIFF=`echo "scale=3; $F - $S" | bc -l` df=`echo "scale=3; $DIFF / $N" | bc -l` is=`echo "...
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1answer
42 views

Comparing variables in arithmetic

Was wondering if someone can take the time to explain the following: I have a directory of files (PDF), which I place into an array. shopt -s nullglob # Set array ...
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1answer
1k views

How can subtract 2 floats which have been extracted from 2 other files with BASH [duplicate]

I'm trying to get the difference between two numbers which I have taken from two files. I think my code will make sense: I've tried to make it work by two different methods, didn't work. What I get ...
4
votes
4answers
2k views

How to sum time using bash?

I want to know the total amount of time that a series of processes would take in my computer to decide if I should running there or in a stronger computer. So, i am forecasting the running time of ...
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votes
2answers
218 views

Integer input constraints

I want to make an input constraint on read: Terminal Shell; read x read y echo $(($x+$y)) I want to make a constraint of x, I want x to be -100 <= x <= 100. What's the command I insert ...
0
votes
1answer
3k views

“too many arguments in [ (test) statement”

this is my first "if-else" script on linux. It gives the error [: too many arguments Code: n=0 if [ $n % 2 -eq 0 ] then echo "even number" fi How to correct it.
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1answer
47 views

Whats wrong in creating/printing this array?

To find the average time taken to create certain files, I'm using this minutes array, then would simply use bash arithmetic to find the average. However I'm unable to get the difference except for the ...
2
votes
1answer
212 views

Problematic bc calculation in shell script

On Ubuntu 14.04.1 64-bit LTS I am writing a shell script and if I define the start of the sequence used in the for loop with a variable instead of a constant I get really weird behavior and there are ...
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2answers
169 views

How does bash's arithmetic work?

read num1 2 read num2 5 echo "$((num1+num2))" 7 echo "$(($num1+$num2))" 7 I referred this. I don't understand how the above both expressions yields same result? Please explain. echo "$[...
3
votes
3answers
7k views

Calculate and divide by total with AWK

Given the following data file... foo 10 bar 20 oof 50 rab 20 ... how would I print column two as a percent of the total of column two? In other words, I want... foo 10 10% ...